The present invention relates to wireless, or free space, communication. Particularly, the present invention concerns channel discrimination techniques suited for wireless free space interconnects.
Reliance upon wireless technology is increasing as the need to increase computational efficiency becomes salient. Specifically, improved operational characteristics of data links employ advancements in wireless communication systems to replace conventional hardwired technology. A well-known example includes the replacement of conventional hardwired telephony with wireless cellular technology. This has generated a need for improvement methodologies that move away from traditional RF wireless technology to optical technology.
U.S. Pat. No. 4,057,319 to Ash et al. discloses an optical interconnect system in which individual connections are made involving the passage of light between a specific device in one array of optical devices and a specific device in another array of optical devices. This is achieved via a phase hologram plate of the transmission type fixed relative to each array.
U.S. Pat. No. 5,140,657 to Thylen discloses a device for optically coupling an optical fiber, forming part of an optical communication system, to an optical semiconductor laser amplifier. Specifically, the semiconductor laser amplifier has an input facet and an output facet, and the optical fiber has an end surface arranged opposite to at least one of the facets. A diffraction optics element is disposed between the end surface of the fiber and the surface of the facet in order to adapt the nearfield of the fiber end to the nearfield of the facet surface while filtering the same to reduce spontaneous emission noise. The diffraction optics element is described as being a phase hologram.
U.S. Pat. No. 6,072,579 to Funato discloses an optical pickup apparatus that includes first and second light sources that selectively emit one of first and second light beams, respectively. The first and second light beams are different in wavelength and are suitable for accessing first and second optical disks respectively. A coupling lens converts a corresponding one of the first and second light beams into a collimated beam. An objective lens forms a light spot on a corresponding one of the first and second optical disks by focusing the collimated beam. A holographic optical element receives a reflection beam of the light spot from one of the first and second optical disks and provides holographic effects on the reflection beam so as to diffract the reflection beam in predetermined directions of diffraction depending on the wavelength of the reflection beam. A photo detector receives the reflection beam from the holographic optical element at light receiving areas and outputs signals indicative of respective intensities of the received reflection beam at the light receiving areas, so that a focusing error signal and a tracking error signal are generated based on the signals. A drawback with the aforementioned optical interconnect systems is that each coupling device requires precise alignment of the optical elements to achieve efficient coupling of optical energy while avoiding cross-talk between adjacent channels.
What is needed, therefore, is an improved free space interconnect technique that reduces cross-talk between adjacent channels.